The heat seal quality of the composite bag has been one of the most important items in the packaging manufacturer's control of product quality.
The following is the heat sealing process of the factors:
1, Packaging Bag the type of heat sealing layer material, thickness and quality of the heat sealing strength of a decisive impact.
General composite packaging commonly used heat sealing materials are CPE, CPP, EVA, hot melt adhesives and other ionic resin co-extruded or blended modified film. Heat sealing layer material thickness is generally between 20 ~ 80μm, under special circumstances also have up to 100 ~ 200μm. The same heat sealing material, the heat sealing strength increases with the thickness of the heat seal increases. Cooking bag heat sealing strength of the general requirements of 40 to 50 Newton, therefore, Packaging Bag the heat sealing material thickness should be 60 ~ 80μm or more.
2, the heat sealing temperature on the heat sealing strength of the most direct.
The melting temperature of various materials directly determine the minimum heat sealing temperature of the composite bag. In the production process, Packaging Bag the heat sealing temperature is often higher than the melting temperature of the heat sealing material due to the heat sealing pressure, the bag making speed and the thickness of the composite substrate. The smaller the heat sealing pressure, Packaging Bag the higher the heat sealing temperature; the faster the machine speed, the thicker the composite layer of the composite film, the higher the heat sealing temperature required. If the heat sealing temperature is lower than the softening point of the heat sealing material, it is impossible to seal the heat seal layer no matter how the pressure is increased or the heat sealing time is prolonged. However, if the heat sealing temperature is too high, and easy to damage the welding edge of the heat sealing material melt extrusion, resulting in "root cutting" phenomenon, Packaging Bag greatly reducing the sealing heat sealing strength and bag impact resistance.
3, to achieve the desired heat sealing strength, a certain pressure is essential.
For thin bags, heat sealing pressure to achieve at least 2kg / cm22, and with the composite film increased the overall thickness of the corresponding increase. If the heat sealing pressure is insufficient, between the two thin film is difficult to achieve the real fusion, Packaging Bag resulting in local heat sealing is not good, or difficult to catch the gap in the middle of the weld bubbles, resulting in Weld; of course, the heat sealing pressure is not bigger Well, should not damage the welding edge is appropriate, because the higher heat sealing temperature, the welding edge of the heat sealing material has been in the semi-molten state, too much pressure to squeeze part of the heat seal material, so that the edge of the weld Semi-cut off the state, the weld brittle, heat sealing strength decreased.
4, heat sealing time is mainly determined by the speed of the bag machine.
Heat sealing time is also a key factor affecting weld seal strength and appearance. The same heat sealing temperature and pressure, heat sealing time is long, Packaging Bag the heat sealing layer fusion more fully, combined with more solid, but the heat sealing time is too long, likely to cause wrinkles wrinkles, affecting the appearance.
5, heat sealing after the weld if the cooling is not good, not only will affect the appearance of the weld smoothness, but also on the heat sealing strength have a certain impact.
The cooling process is through a certain pressure, with a lower temperature just after the heat sealing of the weld to shape, to eliminate the stress concentration process. Therefore, the pressure is not enough, cooling water circulation is not smooth, the amount of circulation is not enough, the water temperature is too high, or cooling is not timely will cause poor cooling, heat sealing edge Alice, heat sealing strength.
6, the more the number of heat sealing, heat sealing the higher the strength.
The number of longitudinal heat sealing depends on the effective length of the longitudinal bar and the ratio of the length of the bag; Packaging Bag the number of transverse heat sealing is determined by the number of groups of transverse heat sealing devices. Good heat sealing, requiring the number of heat sealing at least twice. General bag machine hot knife has 2 groups, and hot knife position overlap the higher the degree of heat sealing effect the better.
7, the same structure and thickness of the composite film, the higher the peel strength between the composite layer, the greater the heat sealing strength.
For the lower peel strength of the product, the weld is often broken at the weld of the composite film between the first layer of separation, resulting in the inner surface of the heat seal layer to withstand the tensile strength, and the surface material loss of reinforcement, the weld heat sealing The intensity is greatly reduced. If the composite peel strength is large, it will not occur between the edge of the interlayer peeling, the measured heat sealing strength is much greater.